DE1512172A1 - Frequency wave synthesizer - Google Patents

Description

PATENT LAWYERS '* ■ *' * · '' * ·

DR. MOLLER-BORt ■ DIPL.-ING. GRALFG

DR. MANSTZ · DR. DEUFEL Munich, 9O. Shark 1967

Γ --- "NCKEN 22, ROBEFT KOC:; - GiR. 1 Tj ^ / Q, _P P

C. I. T.

COMPAGNIE INIXJSTRIELLE DES TELECOMMUNICATIONS 12, rue de la Baume, Paris (8 °), France

3? E equine wave synthesizer

The invention "relates to a wave synthesizer, in particular for waves frequency-modulated by telegraph signals, with devices for limiting the spectrum and reducing telegraphic distortion is equipped and suitable for applications -ler technology of the integrated Circuits is suitable.

The advantage that the telegraphic transmission through frequency-modulated Waves offers, among other things, good protection against noise and interference. If the However, transmission without appropriate measures will deliver they have a very broad spectrum that can cause crosstalk and overload the filters on the receiving end.

The frequency modulation between a rectangular basic frequency _{wave F 1} with "rest" value and an identical basic frequency wave F ₂ with "work" value (F ₁ <F ₂ ) of class "1/1" for the duration of a telegraphing step M results in a spectrum of spectral lines offset by f (f = 1/2 M), which _{are grouped around the frequencies F Q} , 3F _Q , 5F _Q etc., where F _{Q is} equal to (F ₁ + F ₂ ) / 2.

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Such a spectrum accordingly consists of a first series F _Q + nf, a second series 3P _Q + nf, a third series 5F + nf of spectral lines, etc .; η denotes a variable integer. As is known, by appropriate sieving, the higher order spectral line series can be reduced to negligible amplitudes and only the first series P ₀ + nf can be retained.

On the other hand, it is important that the characteristic time occurring at any point in the half-change of the carrier wave neither leading nor lagging. If the phase of the carrier wave is affected by the modulation, it may - as shown below - a considerable telegraph distortion occurs:

Given z. B. a _{transmission channel standardized with P 1} = 1300 Hz and Pp = 2100 Hz, ie a period T ... '- ^ 765 μ3 and a period Tp m 475 us at a telegraphing speed of 1200 baud. The duration of a telegraph step is 1/1200 - ^ 835 μ3. The deviation of the characteristic time can be a maximum of 1 * 2 , i.e. 1240/2 = 620 μβ

2
In relation to a step of 835 ^ s duration, this possibly results in an impermissible maximum telegraph distortion £ of 620/835 = about 75 percent.

When the frequency is multiplied by the ratio k, the number of periods and thus the telegraph distortion are reduced in the same proportion. A multiplication by, for example, 30 (k = 30) results in a perfectly permissible distortion of maximum 75/30 = 2.5 percent.

On the other hand, when the frequency is increased, the necessary or advantageous screening becomes simpler and easier more economical.

The advantages of a relatively high frequency modulation are accordingly justified. As is known, the conversion is carried out with an auxiliary carrier frequency at normal frequencies; it must but then the problem of low-frequency sieving, which one just wants to avoid, can be solved.

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If, on the other hand, a very highly stabilized, i.e. expensive, oscillator is used for the subcarrier frequency, the aleatoric fluctuations ^ f of the frequencies F .. and Fg are ^{reduced to} a lower frequency level, so that the fundamental frequency fluctuations ^ t / t are relatively increased in value. If a less expensive oscillator of medium stability is used to generate the subcarrier frequency, the relative value of the fluctuations is amplified by the additional fluctuation in the subcarrier frequency.

Ee is therefore more advantageous to undertake such a frequency lowering by frequency division in which the relative fluctuation value £ f / f is retained. In the technology of printed circuits, which uses only logic circuits and no transformers or inductors, the frequency division is known to take place with the help of an electronic counter, the end element of which changes its position k times slower than the signals triggering it, i.e. once per k received signals or once per k periods of the control signal.

In the case of telegraphic transmission with a relatively high scanning speed in relation to the carrier frequency, such a frequency division cannot be used because the The occurrence of the characteristic time shifts over the course of a period. As already mentioned, this can be temporal Postponement lead to excessive telegraph distortion.

The frequency division must therefore be carried out according to a method in which the determination of the characteristic time is maintained by the multiple frequency, d. H. an underfrequency must be generated that has just as many phase steps has as there are multiple frequency periods in an underfrequency period, i.e. k phase steps per multiplication or division by or by k.

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According to the invention, this is done by synthesizing a frequency wave F, which _{can assume two values F .., F 2} , with the aid of a; Circuit achieved, comprising the following devices: a kF frequency oscillator, where k is an even multiple of η, a known up and down counter of the capacity (n - 1) with an input and two control terminals, a decoder with η outputs, an analog-to-digital converter that delivers an output voltage proportional to A + sin ^ j , where A is a constant and i = 0,1, ... n-1, as well as logic circuits connected to the decoder for triggering the The counter counts up as soon as it reaches the "0" position and counts down as soon as it has reached the "n-1" position.

The invention is based on exemplary embodiments below Described with reference to the accompanying drawings; in these

1 shows an overview circuit diagram of a first embodiment of the device according to the invention;

FIG. 2 is a graphic representation of the curve of the current tapped at the output of the device according to FIG as well as the additional curves;

3 shows an overview circuit diagram of a second embodiment;

FIG. 4 is a graphic representation of the curve of the current tapped at the output of the device according to FIG. 3 and of the current Additional curves.

In Fig. 1, 1 denotes a telegraph signal generator, 2 denotes an 'RC forming filter and 3 denotes a linear oscillator, the frequency of which changes linearly depending on the strength of the signal applied to the input, e.g. B. a

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Tilting generator or multivibrator, which is roughly rectangular Supplies waves, the frequency of which is a linear function of a control voltage applied to an output terminal. 4 designated an OR circuit, 5 a "bistable multivibrator, 6 a Binary counter, its two control inputs 61, 62 to two outputs 51, 52 of the flip-flop are connected. The counter 6 counts via these connections in a first state Tilt stage forward and backward in their second state. Two-way counters are known in the art. For 16 counting levels from 0-15 inclusive, the counter 6 has, for example, 4 toggle stages. 7 denotes a decoder that uses the Outputs i = 0, 1, 2, ... 15 voltages to an analog ^

Digital converter 8 supplies, which has a sin proportional w

Output voltage V emits. This voltage V is fed to the input of the amplifier 9, which via an output terminal S supplies a voltage U. In this case the constant A is at least equal to one.

The outputs (0) and (15) of the decoder 7 are via the OR circuit 4 at the input of the flip-flop 5. If a voltage occurs at the output (0) of the decoder, the flip-flop 5 flips the Counter 6 in the count-up state; If a voltage occurs at the output (15), the flip-flop 4 switches over and displaces the Counter 6 in the down counting state. When the We'llen delivered by the multivibrator 3 one after the other at the input of the counter - lers 6 arrive, it goes into counting states ™ one after the other 0, 1, 2 ... 15 and 15, 14 ... 0 over.

Fig. 2 shows, in the graphic representation a, a telegraph signal which changes from the “work” value to the “rest” value _{at time t 1.} The "work" value corresponds to a higher frequency F ₀ and the "rest" value

1 1

a lower frequency F ₁ (Fp - ψ- and F ^ = ψ-).

The graphic representation b in FIG. 2 illustrates the pre-thrust signals arriving in the counter 6. At time t .. the frequency value changes; However, there is no phase incoherence because it is the same oscillator, whose frequency is adjusted from one value to another. 909829/0758

The adaptation takes place continuously, since a linear oscillator is assumed to which a signal rounded off in the pulse shaper 2 is applied. The time span between the individual feed signals can be continuously changed in accordance with the conditions of the pulse shaper 2. This shows the curve c of the actual course of the change F ₀ -> F .;

mm ti

we get as τ_ = 2, τ = 1.

At the output S of the amplifier 9, a current is obtained which basically runs like the curve c in FIG. The one in the amplifier 9 or in one of the subordinate elements of the circuit, the band limitation provides a non-stepped, but sinusoidal current, as illustrated by the dashed line c in FIG.

Any phase incoherence is in the device of Fig. suppressed. The stability of a multivibrator with a frequency tunable according to the voltage does not exceed a certain mean value, for example of about 0.5 percent, so such a system is on channels of lower order, but not applicable to higher order channels; these would result in a frequency deviation that is too high in terms of the absolute value.

In FIG. 3, 11 denotes a telegraph signal transmitter, similar to transmitter 1 in FIG. 1; furthermore: 12 is a logic inverter, one input of which is connected to an output of the encoder 11; 13 a fixed-frequency oscillator F ₁ , 14 a fixed-frequency oscillator Fp. 15 an AND circuit, one input of which is connected to an output of the encoder 11 and the other input of which is connected to the output of the oscillator 13, 16 a further AND circuit, one input of which is connected to the inverter 12 and the other input to the oscillator 14, 17 an OR circuit which receives currents coming from the AND circuits 15 and 16. A binary up and down counter 20 equipped with three flip-flops has one input at the output of the OR circuit 17 and two control terminals at two outputs of a binary flip-flop 19. The three outputs of the three flip-flops of the counter 20 are connected to a decoder 21

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with eight outputs, η = 0, 1, 2 ... 7 connected to the Output of an analog-digital converter 22 generate a sinusoidal voltage sin (w) χ (* / 2).

One input of a differential _{amplifier 26 with the outputs S 1} , S ₂ is at the output of an AND circuit 24 and another input is at the output of an AND circuit 25. One input of each of these two AND circuits is at the common output of the Ümeeimers 22. A Input of the AND circuit 24 '

is with one output of a bistable flip-flop 23 and one input of the AND-Öohaltung 25 is loaded with the other output of the flip-flop 23. The flip-flop 23 is connected to an input at the output of flip-flop 19. Two animal symmetrical output terminals φ S _1, Sg dee differential amplifier 26 aind connected to the terminals of a resistor 27th The outputs (0) and (7) of the decoder 21 are connected to the input of the flip-flop 19 via an OR circuit 18. In this case the constant A is zero.

The graphic representation a in Fig. 4 illustrates the transition of a telegraph signal at time t ^. Before the Time t-. Are the circuits 16 and 15 permeable or '

locked? the frequency Fp supplied by the oscillator 14 (curve b) is fed into the counter 20. After the time t ^ is *

the circuit 16 blocked and the circuit 15 permeable; the frequency F ₁ (curve c) is fed to the counter 20. The äk

The feed signals recorded by the counter are shown in illustration d. By applying 7 signals to the counter 20 in the zero position, the counter moves one after the other to the positions 1 ... , the counter will begin to count, and the following seven signals bring it (7) back into the in a gear position (O). At the zero crossing (O), a voltage occurring in the conductor L triggers the forward operation of the counter 20 and at the same time flips the flip-flop 23 back. This reverses the operation of the differential amplifier 26. The first fourteen after the

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OHIQlNAL INSPECTED

_{Signals recorded as time t Q} (Pig. 4, e) assumed to be zero cause a positive voltage and the fourteen subsequent signals a negative voltage to occur between the output terminals S ₁ , Sp; this process is repeated periodically. The counter counts up during the first seven signals and downwards during the following seven signals, and so on.

In this way, a stepped, or more precisely, one that is smoothed by the band limits in the circuits is created Sine wave without direct current component (dashed curve e). The frequency division factor is 28 for a counter with only three flip-flops and one converter for seven current values instead of one converter for fifteen values as in FIG. 1.

Since the oscillators 13 and 14 work independently, phase incoherence occurs in all cases when changing from frequency F .. to frequency Fp or vice versa at the moment of transition of a telegraph signal; this can lead to telegraphing distortion, as mentioned above. The fluctuations in the occurrence of the transition affect frequencies multiplied by 28; in the case of the frequencies F ₁ = 13C0 Hz and F ₂ = 2100 Hz mentioned in the example, they are approximately 2.7 percent at a telegraphing speed of 1200 baud.

In the embodiment of FIG. 2 with a tilting oscillator modulator and a forming circuit, the linearly frequency modulated low frequency wave has a limited one Spectrum on; a conventional filter can thus be dispensed with.

The examples given apply without restriction and relate to preferred embodiments within the scope of the invention, which apply to other modulation signals as well as to telegraph signals can be applied.

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Claims (4)

PATENT CLAIMS ( 1 Λ synthesizer of a frequency wave F, which can assume two values F .. and Fp, characterized in that it has a kF frequency oscillator, where k is an even multiple of η, an up and down counter known per se the capacity (n-1) with one input and two control terminals, a decoder with η outputs, an analog-digital converter for the output of an A +. proportional output voltage, where A is a constant and i = 0,1, ... n-1, as well as logic circuits connected to the decoder for triggering the up counting by the counter as soon as it reaches the position "0" and the down counting as soon as this has reached the position "n-1", and an output amplifier that emits an output voltage whose envelope curve is a sinusoidal frequency wave F represents. 2. synthesizer of a frequency wave F according to claim 1, characterized in that; that k = 2n and the circuit has an OR circuit connected to the outputs "0" and "n-1" of the decoder and a binary multivibrator, whose outputs are on two control terminals of the meter. 3. A synthesizer of a frequency wello F, characterized in that that k = 2n and the circuit has an OR circuit connected to the outputs "0" and "n-1" of the decoder, whose outputs are on two control terminals of the counter, as well as a second binary multivibrator whose input is on one Output of the first binary flip-flop is, two AND circuits controlled by the outputs of the second binary flip-flop, whose input is at the output of the decoder, and a differential amplifier that has two Inputs is connected to the outputs of the AND circuits. 4. Signal generator for frequency modulation telegraphy with a synthesizer according to one of the claims. 9 0 9 8 2 9/0 7 5 8